Look at it this way: These are the Marvel movies (at whichever studio) that either already have made their way to the big screen or which have been heavily rumored to be in some stage of development more advanced than "gee, wouldn't it be neat if...":
Considering that each Marvel "phase" lasts three to four years, that's 9-12 movies per phase if you go with your 3-per format; 6-8 movies per phase if you go with the current 2-per model. I just listed *32* movies in different stages of development. That's at least 20 movie franchises that just bit the dust right there. Which ones do you think Marvel can afford to lose? And which ones do you think fans will demand the most? Do you begin to see the magnitude of the problem?
Most of these characters can be consolidated into other Marvel films. You're just being greedy...
Ant-Man: Is in production by Marvel
Avengers: Was released and was a huge success
Black Panther: In the pipeline by Marvel
Black Widow: Is part of the Avengers and has cameo's in Ironman 2 and the upcomming Captain America sequel.
Blade: Has reverted back to Marvel but no news on a release/reboot.
Captain America: Has a sequel in production
Daredevil: Was just veverted back to Marvel after sitting at FOX for 9 years.
Deadpool: Had poor portrayal at FOX and has been in development hell since Wolverine: Oringin's
Deathlok: ...........WTF???
Doctor Strange: Is in production by Marvel
Elektra: Still possibly stuck at FOX.
Fantastic Four: Unfortunately being rebooted by FOX. (God help us)
Ghost Rider: Spirit of Vengence was flop. Will likely revert back to Marvel but the damage is already done.
Guardians of the Galaxy: Has a 8/2/14 release date under Marvel
Hulk: Currently part of the Avengers but a sequel is possible.
Inhumans: There was talks of a film but nothing concrete. (Could very well be Marvel's X-men done right.)
Iron Fist: A low budget movie with Luke cage could be done but no news yet.
Iron Man: Has own franchase plus part of Avengers.
Luke Cage: See Iron Fist.
Magneto: He's in every X-men film already. Doesn't even have a solo comic why would he need a solo film...
Man-Thing: Had a cheap film that aired on the Sci-fi chanel. It sucked.
Ms. Marvel: Could feature in Hulk, Ironman films as part of becoming an Avenger. Solo film is not necessary.
Namor: Doesn't need a solo film
Nick Fury: Will be seen in Cap and Avengers sequels. Could cameo in T.V. show a Solo film would be nice.
Punisher: Was just veverted back to Marvel.
Runaways: Meh...Could be featured on the SHIELD show if that. Solo film not necessary.
Silver Surfer: In development hell at FOX.
Spider-Man: Still at Sony. US box office on a continuing downward spiral.
Thor: Film releasing in Nov. this year.
Venom: In development hell at Sony.
Wolverine: Will flop in July.
X-Men: Releasing DOFP on 7/18/14. Success is questionable.